There is a technology for improving an oil holding capability of a sliding surface to thereby improve wear resistance, seizure resistance, and sliding characteristics thereof by providing very small “indentations” having a size of approximately several micrometers, called microdimples, on a surface of a sliding member such as a bearing, which is a part in an internal combustion engine of a transportation apparatus, a rotating machine, and the like.
As technologies of related art for forming microdimples in a sliding surface of a sliding member, there are known technologies, such as shot peening (Patent Document 1), laser processing (Patent Document 2), a combination of laser processing, etching, and microblasting (Patent Document 3), and a method in which a molding die having a plurality of semispherical protrusions arranged thereon is pressed into a resin surface (Patent Document 4).
Further, Patent Document 5 describes a technology for improving adaptivity and durability by providing a sliding member, such as a piston, with a two-layer coating formed of a soft layer and a hard layer made of thermoset (thermosetting) resins, and Patent Document 6 describes a technology for improving wear resistance and seizure resistance of a sliding surface of a sliding member in a transportation apparatus, a rotating machine, and the like by providing the sliding member with very small indentations (recesses, dimples) by laser peening processing to thereby form oil reservoirs.